1. Field of the Invention
The invention relates to a method for heating a low temperature carbonization drum for generating a low temperature carbonization gas, wherein a heating gas conducted in a heating gas circuit is generated by combustion of a partial flow of the low temperature carbonization gas. The invention further relates to a device for carrying out the method and to a low temperature carbonization/combustion plant operating according to the method.
The low temperature carbonization of waste at a low temperature is an endothermic process. The heat required for the reaction is supplied to the waste indirectly through heat exchanger heating surfaces, which are disposed in the form of tubes in the wall of a rotary drum or low temperature carbonization drum.
In a method for thermal waste disposal known from Published European Application No. 0 340 537 A1, a heating gas that is carried in a heating gas circuit is supplied to the low temperature carbonization drum. In a low temperature carbonization/combustion system operating according to that method, the heating gas circuit includes a heat exchanger that is disposed at a combustion chamber of the combustion system, where it absorbs heat energy from the hot flue gas. The low temperature carbonization system is practically always operated together with the combustion system, and the low temperature carbonization gas being generated is combusted in the combustion system to produce steam.
An autonomously heatable low temperature carbonization system is known from German Published, Non-Prosecuted Application DE 30 18 572 A1. In the low temperature carbonization or pyrolysis system described therein, a partial flow of the low temperature carbonization gas being produced is combusted in a combustion chamber. The resultant flue gas is used as heating gas for the low temperature carbonization drum and after passing through a heat exchanger is given off to the environment.
An autonomously operable low temperature carbonization system is known from the publication entitled "Pyrolyse von Abfallen" Pyrolysis of Waste! by Karl J. Thome-Kozmiensky, published by EF-Verlag fur Energie- und Umwelttechnik GmbH, 1985, pp. 97-120, particularly FIG. 2 on page 101 and the text on page 103. In that known system, all of the low temperature carbonization gas being produced is converted into a pure gas in a gas converter with a downstream scrubbing line. Some of the pure gas is combusted in a combustion chamber. The flue gas thus produced is carried to an essentially open circuit and is used as heating gas for the low temperature carbonization drum. However, that method is especially complicated and uneconomical, especially since an already commercially usable pure gas is used for generating the heating gas.